home = new Image();      
home.src = "btn_home_r.gif"; 

calctype = new Image();      
calctype.src = "btn_calctype_r.gif"; 

capital = new Image();      
capital.src = "btn_capital_r.gif"; 

materials = new Image();      
materials.src = "btn_materials_r.gif"; 

year1 = new Image();      
year1.src = "btn_year1_r.gif"; 

year2 = new Image();      
year2.src = "btn_year2_r.gif"; 

year3 = new Image();      
year3.src = "btn_year3_r.gif"; 

year4 = new Image();      
year4.src = "btn_year4_r.gif";